Funds are requested in this application for the University of Maryland School of Medicine to purchase a Philips EM 410-G electron microscope. This insturment is needed to upgrade the existing EM facility in the Department of Anatomy and will also serve as a shared instrument to be used by members of the Department of Physiology. The Department of Anatomy is presently equipped with two Philips EM 201 electron microscopes, one of which is 13-years-old. On the other hand, no electron microscopes are available in Physiology. Neither of the existing instruments in Anatomy offers the basic technical capabilities required by the untrastructural studies being conducted by the Major Users identified in this application. Therefore, the present proposal is based upon an overall need for a third instrument which would increase electron microscope access time for the extensive ultrastructural studies being conducted by the Major and Secondary investigators designated in this application. In addition, a new electron microscope with greater technical versatility is required to enhance the ongoing research activities related to neural tissue and muscle development and regeneration, synaptogenesis, tumorigenesis, epithelial transport mechanisms and structure-function studies of reproductive tissues.